It is known that the junctions between the engine(s) and the mounting pylons are achieved by attaching systems of the front and rear trunnion type, inter alia arranged according to the longitudinal axis of the engine and contained in planes being perpendicular to said longitudinal axis.
In airliners provided with turbojets, the trunnions of the attaching systems are rigid, taking up stresses and torque issued from engines. In addition, with such trunnions, vibrations generated by the latter propagate up to the fuselage inside which the crew and passengers are located. However, thanks to the elasticity inherent to the wings, vibrations are essentially filtered, so that vibrations are hardly experienced by passengers and the crew and thus acceptable. Nevertheless, such vibrations exist and could cause a structural wear of some parts, be amplified mainly at particular frequency ranges, and become a nuisance for passengers and crew members.
If vibrational problems on turbojet airplanes are less obvious, although present, on the other hand, on airplanes provided with turbopropellers, the vibrations are amplified, in particular, at low frequencies, all the more as, in some airplanes designs, the turbopropellers are directly mounted in the wings.
In order to overcome such vibrational phenomena, the trunnions of attaching systems use elastomers so that the latter are less rigid but have a more significant damping than rigid trunnions, allowing for a partial filtration of vibrations, but nevertheless unsatisfactory at low frequency. Indeed, such “flexible” trunnions are submitted to high static loads, involving a high rigidity, in order to limit the movements and the “flutter” phenomena. A high rigidity directly results in a high resonance frequency (depending on the mass as well).
Dampers could also be provided on the attaching systems between the engine and the structure. However, the use thereof does not allow to act on the vibration modes, but to attenuate the effects thereof. In order to be efficient, a damper requires a minimum of movement speed. The current vibrations do not allow such a kind of implementation.